1. Field of the Invention
The present invention relates to an improved isomerization between 3,4-dichlorobutene-1 and 1,4-dichlorobutene-2.
2. Description of the Prior Arts
Heretofore, it has been proposed to heat a dichlorobutene in the presence of an isomerization catalyst of at least one of metal salts of copper, iron, zinc and aluminum.
However, these catalysts have relatively low catalytic activity. Accordingly, it has been proposed to improve the catalytic activity by adding various auxiliary catalysts to the metal salt. For example, an organic amine is added to a copper salt in British Pat. No. 798,889; an organic nitrile is added to cupric naphthenate in Japanese Unexamined Pat. No. 1514/1971; an organic dihydroxyl compound is added in Japanese Unexamined Pat. No. 11560/1972; and an aniline chlorinated derivative is added in Japanese Unexamined Pat. No. 18,808/1972.
As the catalyst for isomerization, it has been required to use a catalyst which has high catalytic activity and which causes less decomposition of dichlorobutene and less by-production of by-products having high boiling point and less corrosion of the apparatus.
The decomposition of dichlorobutene and the by-production of tar by-products having high boiling point cause not only a reduction of the yield of dichlorobutene but also a clogging of the apparatus to reduce the efficiency of the apparatus. When the amount of the catalyst increases, the catalytic activity is usually higher, however, it is preferable to be less amount of the catalyst in view of economy and recovery treatment of the wasted catalyst.
The catalyst having high catalytic activity usually attains the reaction at a low temperature whereby the decomposition of dichlorobutene and the production of tar high boiling by-product can be reduced. When the catalyst is used at a relatively high temperature, it is possible to decrease the amount of the catalyst whereby it is economically advantageous.